The Soil Stack: An Interactive ComputerProgram Describing Basic Soil Science and Soil Degradation S. R. Cattle,*
A. B. McBratney, and D. B. Yates
ABSTRACT Thedegradation of soil in Australiais arguablythe mostimportantenvironmental issue facing that country.Despite the efforts of those in governingbodies andconservationgroups, the educationof youthon this problem is still largelybasedon high school textbooksandoccasionalmediareleases. Withthe emergenceof computersas an alternative modeof teaching, an opportunityhas arisen for educatingyoungpeopleabout soil degradationthrougha medium they find familiar andinteresting. Consequently,a computerprogramdealing with numerous aspects of soil degradationhas beendeveloped.Entitled "TheSoil Stack,"it has a target audienceof highschool anduniversitystudents(16-20yearolds), andis presented a series of cardsgrouped togetheras stacks. Forthose students withlittle or no knowledge of soil science, severalstacks are devotedto background informationon soil, while the bodyof the program deals withthe five maintypes of soil degradation occurringin Australia.In eachof the stacksdealingwithdegradation,an interactivemodelallowsthe user to chooseparameter valuesbeforecalculatingan estimateof degradation. Thisstimulates studentsto experiment withthe variousparameters to determinewhichhavethe greatest effect. Feedbackfromhigh schoolsindicatesthat the program is beingactivelyusedto teach studentssoil sciencesubjects in bothagricultureandgeographycurricula.Theease of use of TheSoil Stack,the interactive models, explanatorygraphics, andwiderangeof topics makeit an interesting andvaluableadditionto the education materialon soil degradation availablein Australia.
B
EALEANDFRAY(1990) point out that almost threequarters of the land in the agriculturally important state of NewSouth Wales is degraded in some way. This degradation is due to manycauses, but the five chief processes are erosion, structure decline, acidification, salinization, and contamination (McBratney, 1991). discussed by Edwards(1991), erosion of soil by wind and water is probably the most obvious form of land degradation, with roadside gullies and duststorms being prime examples. However,the deterioration of soil structure through excessive cultivation is such a significant problem that "in 1989 the Australia GovernmentStanding Committee on the Environmentranked soil structure decline as the most costly form of land degradation in Australia" (McGarry, 1993). Acidification is an increasing problemfor landholders in large areas of the pasture and cropping belts of Australia (Helyar et al., 1988), while salinization of both irrigated and dryland areas cost the country SA550 million ($U.S. 410 million) in 1989 due to lost production and the effective loss of land (Peck, Dep.of AgriculturalChemistry and Soil Science,TheUniv.of Sydney, RossStreet Bldg.A03,NSW 2006,Australia. Received17 Nov. 1993.*Corresponding author (
[email protected]). Publishedin J. Nat. Resour.Life Sci. Educ.24:33-36(1995).
1993). The contamination of urban and agricultural soil by heavy metals (Tiller, 1992) and pesticides (Preece Whalley, 1993) is also becoming apparent. Aside from sporadic media coverage, the education of youth on the threats of land degradation is largely restricted to the often uninvolvinglessons in small sections of high school, technical college, and university courses. With most high schools and all universities having access to computers, however, computer-based instruction is a viable teaching alternative. Such instruction has the advantages of being interesting and involving for the students and easy to prepare for the teachers. The Soil Stack seeks to fill an important niche by offering an integrated package of information dealing with land degradation and somebasic properties of soil (McBratneyet al., 1991). Being a computer program with interactive models, graphics, and moving windows, The Soil Stack can be used equally effectively by individual students or by teachers. Additionally, this programis an ideal tool for the Australia LandCare movementas it strives to educate its memberson various aspects of soil behavior and maintenance. PROGRAMDESCRIPTION The Soil Stack is presented as a series of 13 discrete sections, or stacks: Soil Physical Properties, Soil Chemical Properties, Soil Biology, Soil Formation, Soil Classes, Soil & Civilization, Soil Acidification, Soil Contamination, Soil Salinization, Soil Erosion, Soil Structural Decline, an introductory stack, and a Concluding stack. Each stack is comprisedof a set of cards containing information, graphics, and models. Buttons on each card allow the user to moveforward, backwardand out of a stack; a central MainDirectory card allows the user to quickly moveto different sections. The five stacks dealing with the identified land degradation threats also contain a directory card to facilitate quick movementto areas of interest within those areas. For the sake of comparison, all of the five degradation stacks have been presented in a similar style and order. The directory card in each stack is followed by an introduction, whichprefaces the distribution of the degradation, the different forms of that degradation, causes, control and prevention, an interactive model, and the references used to compile the stack. The interactive modelsallow the user to select a numberof variables that influence the particular type of degradation. A final calculation then reveals the extent of degradation under the conditions selected. This allows the user to experiment with different combinationsof variables and to ascertain which have the greatest effect. The concluding stack serves as a database for students and teachers who require more detailed information on the topics covered in The Soil Stack. Namesand addresses J. Nat. Resour. Life Sci. Educ.,Vol. 24, no. 1, 1995¯ 33
of organizations and institutions involved in land degradation research and soil science are given, reading lists for various topics are given, and several issues related to land degradation are briefly covered. EXAMPLES To illustrate the way The Soil Stack is packaged, a selection of cards from the program is shown (Fig. 1-6). Figures 1 and 2 are the Main Directory cards; these are the focus of the entire stack through which the user can jump from section to section. The card shown in Fig. 1 allows the user to choose any of the introductory soil topics, while Fig. 2 gives the choice of the land degradation stacks and the concluding sections. Figure 3 is an example of a typical information card dealing with a specific topic, in this case, fungi from the Soil Biology stack. The use of background graphics occurs on most cards to hold students’ interest and to let them visualize the subject. The small house icon in the top right corner of this card is found throughout The Soil Stack. Selecting this icon takes the user back to the start of the current stack. The small round button in the top left corner takes the user to a card at the back of that stack that details the references used to compile the information on . that card. Figure 4 is an example of a distribution card
taken from the Soil Salinization stack. A feature of this card is the eye-shaped icon at the top of the card. Selection of this icon takes the user directly to another stack where a closely related topic is discussed, and then brings the user back to the original card. Figure 5 is the calculation card for the Erosion stack model, adapted from the “Soiloss” program (Rosewell and Edwards, 1988), which in turn is an Australian adaptation of the Universal Soil Loss Equation (Wischmeier and Smith, 1978). Each term in the equation (erosivity, erodibility, slope length, steepness, land use, and support practice) is described in the next cards where the user selects one of numerous options for each parameter. For example, on the slope steepness card, the user can select a slope of 0.1, 5 , 10, 15, 20, or 30’70,which is then used in the final calculation. Note the presence of the button, which takes the user to the Soil Formation stack to compare erosion rates with calculated soil formation rates. It should be stressed, however, that these interactive models are for educational purposes only, and should not be used as predictive tools by landowners. Their main function is to illustrate to students what variables affect land degradation and the comparative influence of these variables. Figure 6 is an example of a card from the concluding stacks, and gives information on some of the land conservation programs currently or recently operating in Australia.
Fungi are heterotrophic organisms that are of primary importance in the decay of organic materials in the soil. They can decompose the most resistant organic compounds. like cellulose and lignin. * Some fungi live in close association with roots. These are called mycorrhizal fungi. This is a mutually beneficial relationship. * Most fungi require aerobic conditions and a supply of nitrogen lo thrive, but can tolerate a wide range of pH conditions.
Fig. 1. The first card of the Main Directory: Introductory topics.
Fig. 3. An information card from the Soil Biology stack.
Fig. 2. The second card of the Main Directory: Soil Degradation and Concluding topics.
Fig. 4. The distribution card for the Soil Salization stack.
34
9
J. Nat. Resour. Life Sci. Educ., Yo/. 24, no. 1, 1995
p”,,
Teaching Applications Having been designed for high school, technical college, and university students with access to Apple Macintosh computers, The Soil Stack is ideal as review material for students in earth science courses, or those students with little or no knowledge of soil science and who wish to become acquainted with the subject. The wide scope of subjects covered in the program makes it suitable for students who require reference material for assignments in these subject areas. The ease of use of The Soil Stack also makes it ideal for high school teachers, who can use parts of the program as discrete lessons, set assignments from it, or use it as a reference base. Teachers of courses in geography, agriculture, or geology will find The Soil Stack useful. To date, The Soil Stack has been sent to more than 350 high schoools across New South Wales, as well as numerous colleges and universities around Australia. Responses from teachers have indicated that senior high school students (16-17 year olds) respond more rapidly to this mode of teaching about soil than to the traditional blackboard and textbook approach, and that a greater amount of material can be taught in a given amount of time. Typically, teachers have set quizzes or assignments from The Soil Stack, which the students can only answer fully by going through the program. Feed-
Fig. 5. An example of the calculated soil loss for a unique set of conditions, as predicted by the USLE.
back from universities and technical colleges has indicated that The Soil Stack has been used as a teaching tool for introductory courses and as review material in advanced courses. The universality of the subject and the ease of programming in HyperCard also means that The Soil Stack can be altered to suit audiences outside Australia. Apart from the cards dealing with the distribution of degradation and those detailing further information, few changes would have to be made to make the program suitable for students elsewhere in the English-speaking world. Similarly, upgrading The Soil Stack to report on recent developments in soil science or degradation issues would be a simple case of inserting new cards into the existing stack. Such an example could be the conversion of the USLE-based erosion model to a RUSLE-based (Revised Universal Soil Loss Equation, Renard et al., 1991) model, although the various contributing factors have not been fully calibrated to Australian data as yet. SOFTWARE AVAILABILITY AND SPECIFICATIONS The Soil Stack is run using the HyperCard program on an Apple Macintosh computer. To enable The Soil Stack to function fully, HyperCard Version 2.1 (or later) should be installed on the computer before use, and the Macintosh must be running System 6.0.7 (or later). The Soil Stack is supplied as a set of four floppy disks, and can be used as such if the user's machine lacks a hard drive. The more efficient method of running the program, however, is to load the entire stack onto the Macintosh hard drive, which avoids disk-swapping to reach all sections of the program. The Soil Stack requires about 3 Mbytes of disk space for storage. As production of The Soil Stack was funded by the New South Wales government, copies of the program were sent free of charge to schools in that state. For other prospective users, however, the cost of the four floppy disks and manual is $A 85 ($U.S. 65). Orders or enquiries should be made to: The Soil Stack, Department of Agricultural Chemistry and Soil Science, The University of Sydney, NSW 2006, Australia. ACKNOWLEDGMENTS We acknowledge the significant contributions of J.B. Stewart, P.E. Tolmie, J.G. Walsh, S.R. Young, and K.L. Elton, authors of sections of The Soil Stack.
|[cluJ
